Decentralized trusted timestamping based on blockchains is used to protect a large variety of digital data. At present, in the case of trusted timestamping services, such related information is not included in the OP_RETURN field of a Bitcoin's transaction chain, which has a limited size (40 bytes). When OP_RETURN is extended, (e.g., with multiple OP_RETURN fields) the transaction is rejected by the Bitcoin network. We propose storing data in the blockchain by encoding into Bitcoin addresses. The transactions created by the proposed method are similar to the usual transactions; therefore, they will not be rejected. The proposed method expands the storage space to a maximum of N*20 bytes, thereby enabling the storage of additional information (e.g., file names, creator names, and keywords) as well as file hashes. We performed experiments with a picture and its copyright information. We set N =3, resulting in storage of 60 bytes of data. The experimental results indicate that the proposed method can timestamp a file in an average of 24 min at a possible cost of 0.24 USD. We believe that the proposed method can prove the existence and integrity of a digital file, which is helpful in copyright protection.
Many challenges are encountered when uninterruptible power supply (UPS) modules are operated in parallel to meet the power demand of the load. The circulating current is one prominent example of these challenges that may cause serious damage to equipment. Hence, control algorithms must ensure that the current is shared equally or in proportion to the power ratings of the parallel inverters, while mitigating the circulating current. Another challenge is that all parallel inverters should have equal output voltage, phase, and frequency. This paper proposes a new method to control parallel UPS modules. The method is based on regulating the capacitor voltage of the LCL output filter of each inverter to indirectly control its output current. The method can achieve high accuracy in terms of equal current distribution between the power sources. Simulation and experimental results are presented to verify the theoretical analysis.
This paper proposes a new capacitively isolated multicell dc-dc transformer (dcx). The proposed dcx consists of dc-dc cell converters with pairs of isolation capacitors that substitute for high frequency transformers. The capacitively isolated cell converter achieves higher efficiency compared with the conventional inductively isolated dc-dc converter because of no transformers. The multicell approach also accomplishes the various voltage transformation ratios based on the input-series-and-output-parallel and input-parallel-and-output-series connections of the cell converters, overcoming the drawback of the capacively isolated converter with the fixed voltage transformation ratio. The analysis of the isolation voltage-sharing across the capacitors was conducted to show the feasibility of the proposed multicell dcx. The prototype of the 96V-24V, 200W dcx using two 48V-24V, 100W capacitively isolated dc-dc cell converters was also fabricated to confirm the validity of the analysis. The proposed approach contributes to the achievement of highly efficient and scalable power converters to realize future low-carbon societies.
This paper addresses the joint limit avoidance problem in kinematic control of redundant manipulators. A kinematically redundant manipulator has more Degrees of Freedom (DOFs) than are required to perform a given task. An inverse kinematic problem for such a manipulator admits an infinite number of solutions. In its kinematic control, by utilizing the redundant DOFs of the solutions, we can compose a primary task in consideration of a constraint condition. We usually select one of the solutions by introducing a Performance Criterion Function (PCF). The PCF performs a secondary task that has no effect on a primary task. Thus, we can introduce, e.g., joint limit avoidance as a secondary task to the design of a PCF. However, it is hard to perform joint limit avoidance in the case where a joint behaves in the close vicinity of the limit. In this paper, we propose a new PCF for avoiding joint limits. The main feature of the function is to admit the joint range of motion maximally. We adopt the proposed function in the gradient projection method to obtain the redundancy resolution. The effectiveness of the function is demonstrated by both numerical and experimental results. The differences among the proposed and conventional functions are also discussed.
Designed to help the driver avoid hazardous situations, driving assistant technology can be seen as an intermediary step between cars controlled by humans and automated cars. Its capacity to reduce the number of casualties on the road and its better acceptance from users compared to autonomous technology make it an interesting field of research. One crucial aspect of a safe driving behavior is the avoidance of involuntary lane changes. This situation can occur if the driver does not pay attention to his task or in the case of high-speed driving. However, lane changing can also be desired, and the driving support should then help the driver. This paper describes a proposal for a line crossing active assistant. After realizing road surface marking extraction, virtual potential fields are created from the lines defining the road lane. Assistive torques are then applied to the steering wheel and pedal of the controlled car. The intensity of the effect of this support is modulated as a function of the situation by a fuzzy logic algorithm. Finally, results obtained under real conditions tests are discussed and analyzed.
Vehicle detectors play an indispensable role in traffic management and control systems (TMCS). The data collected via vehicle detectors are used to fulfill various functions such as signal control and traffic information provision. In Japan, TMCS use mainly ultrasonic detectors. Owing to their aged deterioration, their detection accuracy gradually reduces over many years, and thus their efficient operation and maintenance requires accomplished engineers. In recent years, it has become difficult to maintain great numbers of ultrasonic detectors because of the financial constraints in public resources and shortfall of accomplished engineers. In this paper, we propose failure detection methods, and confirm their validity by using actual data. First, we propose an aggregation method of detector data for classifying installation positions, and validate the method by using large amount of data. Moreover, we propose a few failure detection methods with the aggregated data, and compare their decision results by using the actual data.